Sometimes not receving alerts for a DXCC

I currently have Ham Alert set up for certain DXCCs on certain bands, but I notice that I am sometimes not getting a notification even though the desired DXCC will appear in the cluster. Note that I am using the DXCC and not the call sign. A reason/ correction for this behavior would be welcome and thanks in advance.

Are you able to provide examples?
Without further information, it is impossible to analyze this.
DXCC, band, date, time,…

It took a while, but I have a fresh example. I have a filter set up to receive Guadeloupe (TO1Q) for 17m SSB. Although the desired station appeared in the cluster, I received no alert. I have attached screenshots of both the cluster and my trigger settings. Note that I tried both the direct call and then the DXCC like I am using now to no avail. No alert was received in either case.

Thanks for the example. According to the server logs, that spot was delivered to you (among others):

So I’m inclined to believe that something went wrong on the Telnet client side, which is the only action that you have enabled for that trigger. It could be an idle timeout issue – before the 19:05 spot, there were no spots sent to you for slightly more than an hour. Some firewalls/routers/CGNAT implementations terminate idle TCP connections after a short time, sometimes only 5 minutes. When the connection is shut down uncleanly (and most firewalls simply delete the state table entry, without notifying the client or server), it can take a while for the Telnet client software to notice. If a spot comes in during this interval, it will not be delivered to the client. The client software could issue a “sh/dx” command after reconnecting to grab the last 20 spots or so to catch up, but not all clients do this.

What I’ve just done is enable server side TCP keep-alives with a one minute interval, in an attempt to stop intermediate firewalls from breaking idle connections. Hopefully it works…

If you have important spots that you don’t want to miss, then I’d suggest also enabling the App action to get those on the HamAlert app, which does not have these idle timeout issues.

Thanks. I was afraid it was something on my end. Unfortunately, my ways of receiving the feed are limited. I don’t own any cell or smart phones and therefore no apps and that leaves what I can get via Ubuntu. I use a program for logging which also has a Telnet interface but may not be very good as the program is old and hasn’t been updated for some time (PyQSO). I would welcome any suggestions for Linux utilizing Telnet effectively.